The invention relates to an aircraft comprising a cabin space dedicated to the passengers and, underneath, an under-cabin space housing systems able to carry out functions necessary for the operation of the aircraft.
Most commercial aircraft comprise a nose housing a cockpit, a tail and, between the two, a central part. This central part situated in the pressurized zone of the fuselage comprises a cabin space dedicated to the passengers and, underneath, an under-cabin space.
The under-cabin space or hold conventionally contains both containers for transporting freight and various systems necessary for performing various functions, for example electrical, electronic and avionic functions (electrical master boxes and associated computers, avionics computers, etc.), aeraulic functions, notably in terms of the air conditioning and ventilation of the various pressurized zones of the fuselage (for the sake of the comfort of individuals and operation of equipment) and hydraulic functions, notably in terms of the distribution of water for the spaces dedicated to restauration and the toilets and to collecting the wastewater from these spaces.
It is known that these systems, or at least some of them, are distributed through the under-cabin space in equipment disposed within various dedicated technical zones, namely:                a forward main electrical and electronic technical zone situated both in the nose and in the central part,        a central auxiliary electrical and electronic technical zone situated in the central region of the central part where the wing structure of the aircraft is connected to the fuselage in said central region,        an aeraulic technical zone situated to the rear of the central auxiliary electrical and electronic technical zone,        a rear auxiliary electrical and electronic technical zone situated in the rear region of the central part,        a hydraulic technical zone situated to the rear of the rear auxiliary electrical and electronic technical zone and before the tail.        
It will be noted that the principle behind the geographical dispersion of the various technical zones also applies to aircraft in which the wing structure is positioned differently. The siting of these technical zones may therefore vary.
Integrating the various electrical, electronic, aeraulic and hydraulic systems into the equipment of the aforementioned dedicated zones respectively leads to complex installations.
Specifically, this integration needs to take into consideration:                on the one hand, installation constraints which make it difficult if not to say impossible physically to integrate objects of different shapes and types into a single location, and        on the other hand, safety constraints which require at least some of the systems to be duplicated by installing two of the same systems as far apart from one another as possible.        
Moreover, because of these constraints, the functional connections between the systems (electrical, aeraulic, hydraulic connections) are not optimized in terms of their lengths and complexity.